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I know of no such thing as the 'Cretaceous-theory'!

However you probably mean the The Cretaceous-Tertiary extinction event, which occurred approximately 65.5 million years ago.

If this is the case then, the theory regarding this is that, a comet or asteroid (an impactor) hit the Earth at this point and caused the extinction event.

Impactors frequently contain levels of the element iridium not found in normal Earth rocks, and a worldwide distributed spike in the iridium content of a specific geological layer would seem to support the fact that an impactor had a global affect.

However please note, that while much is made of the impactor theory for the extinction of the dinosaurs, the most recent geological research seems to prove definitively that dinosaurs were present on the planet for some hundreds of thousands of years after the iridium spike and thus, while the impactor certainly happened, it is not directly responsible for the demise of the dinosaurs.

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15y ago

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